1. Field of the Invention
The present invention relates to a controlling apparatus and more particularly to a controlling apparatus, such as an inverter, which has been arranged for ease of wiring and handling.
2. Description of the Background Art
Inverters have become important to machine systems used in various industrial fields, particularly as a speed control apparatus for motors in such machine systems. Often, in complex systems employing plural motors, several controllers are mounted together on a common panel in a confined space, necessitating designs that minimize the area required for installation and wiring yet permit easy access for maintenance and repair. However, in direct conflict with this goal, a larger number of functions with greater sophistication have been added to inverters. Even though further reductions in the inverter size may be possible as chip functions are integrated and chip size is reduced, certain basic requirements prevent the panel arrangement for plural controllers from becoming compact.
An inverter unit consists of a main circuit printed wiring board (PWB) with heat generating components such as diode modules and transistor modules that usually are mounted on a PWB rear side, and capacitors, connectors, protective function circuit components and terminal blocks that usually are mounted on the PWB front side. The main circuit PWB is fixed to the inside of an aluminum die casting chassis that is constructed with heat radiation fins, acting as a heat sink. Since the base surfaces of the heat generating diode modules and transistor modules, which are installed on the rear side of the main circuit PWB, are in direct contact with the inside surface of the metal chassis, heat generated by the modules will be conducted through the chassis and radiated from the heat sink structure which extends from the chassis.
Also forming a part of the inverter unit are electric components which constitute a control circuit on a control circuit pWB. The control circuit PWB has terminal blocks for external wiring connection and is installed on the top side of main circuit PWB. Further, an option circuit PWB also may be installed on the top side of the control circuit PWB. This arrangement of main circuit PWB, control circuit PWB and optional function PWB are often arranged in three stages.
Finally, a cover to protect the PWB components ordinarily is installed on the chassis.
External cable connecting terminals are mounted on the bottom side of each printed board and are arranged in the order of main circuit PWB, control circuit PWB, and option circuit PWB. The terminals on a lower PWB usually has a shorter length than those on a PWB above, and the terminal blocks are placed on the side of each PWB. This arrangement presents great difficulty for the connection of a large number of wires to a single controller and the arrangement of a plurality of controllers on a single panel. This difficulty can be better understood from a consideration of the sizes and numbers of wires that must be connected to a conventional controller with presently available functions.
The number of external cable connecting terminal blocks and cable sizes for 200 V 3.7K inverters are as follows:
______________________________________ number of terminals cable size ______________________________________ main circuit 9 3.5 mm.sup.2 (AWG12) terminal block control circuit 30 0.75 mm.sup.2 (AWG18) terminal block option circuit 28 0.75 mm.sup.2 (AWG18) terminal block ______________________________________
When every function is added to the inverter unit so that it can be used in every possible field as an industrial machine system, the product will become very complicated. Depending upon the way such unit actually is used, unnecessary functions may be provided. To avoid this problem, the control circuit PWB is equipped with certain basic functions which are commonly used and the option circuit PWB is provided with functions which will serve only for specific purposes. By selectively combining a customized option circuit PWB with a inverter unit main body, an efficient and economical inverter unit which is appropriate for specific applications, will be provided.
FIG. 13 is a schematic circuit diagram of an inverter unit 51, which is connected to a source of power via plug connectors 55A and to a motor M via connectors 55B for controlling the operation of the motor M. A main circuit PWB 53 in the unit has a diode module 53A and transistor module 53B at a first level. A control circuit PWB 54 is connected by wires to the main PWB and has terminals 56 for external connection. Optional circuit PWB modules 63A and 63B are connectable by a connector 64 to the control circuit PWB 54 and have external terminal blocks 65.
FIG. 9 is a plan view of an inverter unit known in the art. FIG. 10 is a sectional view taken along the plane 10--10 of FIG. 9.
In this inverter unit 51, a main circuit printed wiring board 53 and a control circuit printed wiring board 54 are contained and secured in an aluminum diecast chassis 52. The main circuit printed wiring board 53 and control circuit printed wiring board 54 are arranged in two stages. The main circuit PWB 53 is disposed in the lower position and the control circuit PWB 54 in the upper position. Within the chassis 52, the bottom of the main circuit PWB 53 is lower than that of the control circuit PWB 54.
A main circuit external cable connecting terminal block 55 is disposed and secured on the bottom of the main circuit PWB 53 which is exposed under the control circuit PWB 54
A control circuit external cable connecting terminal block 56 is disposed and secured to the bottom of the control circuit PWB 54.
A cover 57 is a protective cover for electronic components mounted on the control circuit PWB 54. A wiring cover 61 shown in FIG. 10, which is installed to the area of the main circuit external cable connecting terminal block 55 and control circuit external cable connecting terminal block 56, is removable as shown in FIG. 9.
Main circuit external cables 59 are all connected to the main circuit external cable connecting terminal block 55. Control circuit external cables 60 are all connected to the control circuit external cable connecting terminal block 56.
A rubber bushing 58 is fitted in an installation hole formed in the bottom side face of the chassis 52.
In the inverter unit 51, the main circuit external cables 59 for power supply, motor, etc. are directed into the chassis 52 through the rubber bushing 58 and the leading edges thereof are connected to the main circuit external cable connecting terminal block 55. Further, the control circuit external cables 60 for start, stop, speed setting and other signals are led into the chassis 52 through the rubber bushing 58 and the leading edges thereof are connected to the control circuit external cable connecting terminal block 56.
A related conventional design has been disclosed in Japanese Patent Disclosure Publication No. 105903 of 1990.
Another conventional design for an inverter unit is shown in FIGS. 11 and 12. FIG. 11 is a front view thereof and FIG. 12 is a vertical sectional view of FIG. 11. Referring to FIGS. 11 and 12, the numerals 52 to 57, 59 and 60 designate identical parts to those in FIGS. 9 and 10 and such parts will not be described here.
In this inverter unit 62, a main circuit PWB 53, a control circuit PWB 54, and an option circuit PWB 63 for implementing additional functions as an option are housed and secured in an aluminum diecast chassis 52. The printed wiring boards are arranged in three stages; the main circuit printed wiring board 53 is disposed in the lower position, the control circuit printed wiring board 54 in the middle position, and the option circuit printed wiring board 63 in the upper position. For electrical connections, the main circuit PWB 53 and control circuit PWB 54 are connected by a connector or a flat cable (not shown), and the control circuit PWB 54 and option circuit PWB 63 are connected by a connector 64.
Within the chassis 52, the bottom of the main circuit PWB 53 is lower than that of the control circuit PWB 54, and a main circuit external cable connecting terminal block 55 is disposed and secured to the exposed bottom of the main circuit PWB 53.
A control circuit external cable connecting terminal block 56 is disposed and secured to the bottom of the control circuit PWB 54. Similarly, an option external cable connecting terminal block 65 is disposed and secured in a plane (shown as horizontal) defined by the bottom of the option circuit PWB 63, which is connected with the control circuit PWB 54 by the cable or connector 64.
A cover 57 is a protective cover for electronic components mounted over the control circuit PWB 54 and option circuit PWB 63, and forms an opening in the positions of the main circuit external cable connecting terminal block 55, control circuit external cable connecting terminal block 56 and option circuit external cable connecting terminal block 65 so that the terminal blocks are exposed and may be viewed from the outside.
Main circuit external cables 59 are all connected to the main circuit external cable connecting terminal block 55. Control circuit external cables 60 are all connected to the control circuit external cable connecting terminal block 56. Option external cables 66 are all connected to the option external cable connecting terminal block 65.
A bottom cover 67 is designed to fit over the opening and protect the whole inverter unit 62 after the cover 57 is fitted and fixed and the external cables are connected to the corresponding terminal blocks.
In the inverter unit 62, the main circuit external cables 59 for power supply, motor, etc. are led into the chassis 52 and the leading edges thereof are connected to the main circuit external cable connecting terminal block 55. Further, the control circuit external cables 60 for start, stop, speed setting and other signals are directed into the chassis 52 and the leading edges thereof are connected to the control circuit external cable connecting terminal block 56. Similarly, the option external cables 66 are led into the chassis 52 and their leading edges are connected to the option external cable connecting terminal block 65.
As previously noted, conventional inverter units tend to have enhanced functions and the terminals of external cable connecting terminal blocks, particularly those of a control circuit external cable connecting terminal block, are increasing in number. On the other hand, the inverter units tend to be made more compact in size. As a result, if all of the external cable connecting terminal blocks are arranged in one direction as in the conventional inverter unit 51 shown in FIGS. 9 and 10, the number of stages increases and wiring space is reduced. Further, since the wiring gages will vary for different input and output connections of the inverter unit, and the number of terminal blocks is substantial, work on installing and maintaining the inverter unit becomes extremely difficult.
Also, since the control circuit external cables 60 hang down in front of the main circuit external cable connecting terminal block 55, it is difficult to check, for example, the terminal numbers or connected external cable numbers of the main circuit external cable connecting terminal block 55, rendering maintenance and inspection difficult.
The conventional inverter unit shown in FIGS. 11 and 12 also encounters problems. When the option printed wiring board of the inverter unit factory-shipped is to be installed, the cover, etc. must be removed and care must be taken so as not to touch the other parts, for fear of a short circuit other failure. In addition, when an option PWB is to be added after the external cables have been connected, all the external cables must be disconnected, the cover removed, and the option PWB then fitted.